With regard to a rotary roll extruder, heretofore, various kinds of extruders have been proposed, and one example of them (Laid-Open Japanese Utility Model Specification No. 63-13718 (1988)) is illustrated in FIG. 9 and will be explained below.
In FIG. 9, reference numeral 01 designates an extruding roll, and a die head 02 having a flow passageway formed therein towards the circumferential surface of the roll is provided in association with the extruding roll 01. A mouth piece 03 is fixed to the downstream side end edge of the die head 02 as pressed by a mouth piece press member 04.
Material to be extuded 05 fed under a pressure along the flow passageway of the die head 02 comes into contact with the circumferential surface of the extruding roll 01, and it is fed out upwards by rotation of the extruding roll 01.
At this time, the material to be extruded 05 is shaped as a result of passing through the mouth piece 03 having a predetermined shape.
Other examples of the known extruders in the prior art also have a similar structure.
As described above, the rotary roll extruder in the prior art has such a structure that when the mouth piece is to be exchanged, the mouth piece press member is released, and the mouth piece is dismounted in the nearly tangential direction with respect to the roll circumferential surface (in the upper direction as viewed in FIG. 9). Therefore, quick exchange of the mouth piece is difficult.
In addition, the structure is not suitable for performing automatic exchange of the mouth piece, it is difficult to perform an automatic exchange. A known example provided with such an automatic exchange capability has not been proposed.
Furthermore, when the mouth piece has been dismounted, there is nothing to restrain extrusion of the material to be extruded. Hence if an extrusion operation is continued under such a condition, a large amount of material to be extruded would be extruded wastefully, and if more time is consumed for the mouth piece exchange work, then a wasteful amount of the material to be extruded would be increased by the corresponding amount.
Accordingly, it is a common practice to interrupt the extrusion operation upon exchange of the mouth piece, and by the interruption of the extrusion operation normally the material to be extruded would be cut.
In other words, unless the mouth piece exchange is performed after the material to be extruded has been cut, it is difficult to mount a new mouth piece, and if a new mouth piece is mounted while the material to be extruded is kept continued, it must be mounted in such manner that the material to be extruded which has swelled out in the direction of flow may be compressed in the tangential direction with respect to the circumferential surface of the roll. Hence the mounting is difficult, and also in many cases the material to be extruded would be cut after all by the rotation of the extruding roll 01 during the exchange work.
For the above-mentioned reasons, in the prior art upon exchange of the mouth piece the material to be extruded has been cut already. Accordingly, when the extrusion work is subsequently newly performed the tip end of the material to be extruded must be guided, and this necessitates operators' labor.
In addition, once the material to be extruded has been cut, contraction of the end portion of that material to be extruded becomes large. Hence the shape of the extruded material cannot be maintained at a predetermined configuration, and therefore, a certain amount of time is necessary before an extruded material having good quality and precision can be formed stably.
Thus, the known extruder has the shortcomings that a working efficiency of an extruder is lowered in that the material to be extruded is cut upon exchange of the mouth piece, and that essentially an operator is required to intervene.